One technique for the treatment of menorrhagia relates to the ablation of uterine lining using heated fluid which is withdrawn via a return lumen. Such systems are heavily reliant on the maintenance of substantially constant circulating fluid level and flow rate within the uterus to ensure the safety, efficiency and effectiveness of the treatment. Undesirable circulating fluid levels and flow rates may prevent the heated fluid from reaching and properly ablating the entire surface area of the lining of the uterus.